Targeted Phototherapy with Lasers and Other High-Intensity Sources
The concept of targeting phototherapy to the skin involved with disease is attractive for a number of reasons. First, it spares exposure of normal skin and thus reduces adverse effects. Second, in certain diseases such as psoriasis, involved skin has a higher tolerance to UV radiation as compared with uninvolved skin so that higher doses can be used. Third, since the discomfort of an erythema is limited to diseased skin, supraerythemogenic doses may be tolerated by the patient and such doses are known to clear disease faster than suberythemogenic doses. Application of this concept was limited until recently because reliable sources capable of delivering a large dose in a short period of time were not available. This changed with the development of the XeCL excimer laser, which generates 308 nm radiation. Several other high-intensity sources have now become available that are noncoherent and polychromatic.